PSI - Issue 28

Casper Versteylen et al. / Procedia Structural Integrity 28 (2020) 1918–1929 Versteylen/ Structural Integrity Procedia 00 (2020) 000–000

1925

8

Table 4. The maximum values of all alloying element according to ASME XI (2017). Steel grade � (unirradiated) ( ° C ) ∆ �� (forged material) ( ° C ) ∆ �� (welded material) ( ° C ) � (unirradiated) ( ° C ) SA-508 gr.3 -44.4 57.4 85.7 13.0

� (unirradiated) ( ° C )

41.3 18.3

SA-508 gr.4N

-44.4

42.0

62.7

-2.4

3. Results

The CFD simulations were used as temperature input for the FEM calculations. The stress intensity in the wall of the RPV is a combination of the stress due to the fluid pressure and thermal stresses. Those thermal stresses are fluctuating in time and position. The maximum stresses occur on the crack tips, and primarily the crack directly beneath the cooling nozzle, see Fig. 4. The thermal stresses are unpredictable The stress intensity on the crack tip determines the probability for a cleavage crack to occur. The simulated stress intensity factor is compared with the stress intensity factor for cleavage fracture imitation; � � �� � � �2� The critical stress intensity for cleavage fracture is a temperature dependent property. If the calculated stress intensity

Fig. 4.

The stress intensity on the inside of the RPV wall at t = 186 seconds of the cooling transient.